The White House announced the nomination of Lynne Tracy, the current U.S. ambassador to Armenia, to the post after the Russian government signed off on the choice. Such approval is generally routine but couldn't be taken for granted at a time of particularly fraught U.S.-Russian relations over Ukraine, the detention of Americans in Russia, allegations of Russian meddling in U.S. and other elections, and an escalating spat over the staffing of embassies in Washington and Moscow. Tracy, who speaks Russian, previously served as a senior adviser for Russian affairs in the State Department’s Bureau of European and Eurasian Affairs, and...